Reconfigure VS project.

- Moved compilation flag stuff from project file to the abstraction layer.

- Disabled randomized base address as unnecessary.

- Disable stack buffer security check from release.
Align intra buffers to 32 bytes for 256 bit SIMD instructions.
Move optimizations to their own compilation units according to target.

- This is necessary in order to compile AVX intrinsics correctly in
  Visual Studio. Having everything in their own units should also make
  compiling normal C code with optimizations on easier.

- For now the makefile still relies on GCC __target__ attribute for compiling
  intrinsics.